The present invention relates to a device for heating flowing material containing finely divided solids, such as concentrate slurry containing precious metals and/or precious minerals, up to a desired temperature range, for instance to a temperature range used in the treatment process of said material.
The heating of a concentrate slurry containing finely divided solids, such as precious metals and/or precious minerals, up to the temperature range used in the treatment process is usually carried out in a heat exchanger with a hot, liquid medium, such as water or vapor. However, the concentrate slurry is an extremely abrasive and easily settling material which is difficult to treat in heat exchangers. The reason for said difficulty is that the ducts provided in heat exchangers for the flowing of the heated material often are essentially very narrow, and the duct walls are thin. Consequently, in the treatment of concentrate slurries, the heat exchanger ducts wear rapidly off or are blocked, if the flow is too weak in order to carry the solids along with the liquid phase present in the slurry.
The object of the present invention is to eliminate some of the drawbacks of the prior art and to achieve and improved apparatus that is more secure in operation for heating flowing material containing finely divided solids, such as concentrate slurry containing precious metals and/or precious minerals, up to the temperature range applied in the treatment process of said material, when a heat exchanger is employed for heating. The essential novel features of the invention are apparent from the appended claims.
According to the invention, the heating of flowing material containing finely divided solids, such as concentrate slurry containing precious metals and/or precious minerals, up to a desired temperature range is carried out in a heat exchanger that is set in an essentially vertical position. The medium, such as water or vapor, used in the heat exchanger for heating the material is conducted to flow channels that are advantageously installed, apart from the adjusting elements connected to the medium inlet and outlet conduits, in an essentially vertical position, so that the medium used for heating proceeds in the channels from top to bottom. Moreover, the flow channels of the medium used for heating are installed, with respect to each other, so that they are located essentially at regular intervals. In addition, the flow channels are advantageously provided, at least as regards the surface that gets in contact with the heated material, with a particular wearing element, which further reduces the wearing effects of the material to be heated. In shape, the flow channels are advantageously tubular, but they can also have some other shape, for instance rectangular or square in cross-section.
In the apparatus according to the invention, the flowing material containing finely divided solids, such as concentrate slurry containing precious metals and/or precious minerals, is fed from bottom to top, essentially in a vertical position in between flow channels contained by the medium used for heating, and consequently in the opposite direction with respect to the flowing direction of the heating medium. With respect to each other, the flow channels of the heating medium are installed so that the material to be heated is maintained in suspension, which prevents the classification of said material. Thus the transversal flowing area of the flowing space of the material to be heated and the transversal flowing area of the flow channels of the heating medium are mutually matched in order to keep the material to be heated in suspension essentially throughout the heating process. The flowing of the material to be heated is advantageously turbulent, but when the flowing takes place essentially vertically upwards, the settling of the solids contained in the material to be heated does not occur as easily as in a corresponding, essentially horizontal flow.
The flow channels of the heating medium used in the apparatus according to the invention are advantageously interconnected to form a flow channel system, so that said flow channel system can be connected to the housing element of the apparatus according to the invention, advantageously by a flange joint, for example. Thus the connecting of the flow channel system to the apparatus housing also constitutes part of the support structure of said apparatus. When the flow channel system is attached to the housing element by a flange joint, it can easily be detached from the housing when necessary, for instance for possible maintenance of the flow channel system.
In the flow channels of the apparatus according to the invention, there is advantageously maintained a pressure that is higher than at least the hydrostatic pressure of the material to be heated. This prevents, in the event of possible damages, the access of the material to be heated to the flow channels consisting of the heating medium. When desired, also that part of the apparatus according to the invention that contains the material to be heated can be pressurized. In that case, when defining the pressure to be maintained in the flow channels, also the pressure in the part that contains the material to be heated must be taken into account.
In order to feed the material to be heated into the apparatus according to the invention, in the bottom part of the apparatus, advantageously underneath the heating medium flow channel system, there is provided a feed chamber, and the walls of said feed chamber are, at least as regards the sections that are in contact with the material to be heated, essentially equally thick as the walls of the flow channels, and advantageously coated with some wear-proof material. On the bottom of the feed chamber of the material to be heated, there is advantageously attached an adjusting element, such as a valve, in order to adjust the medium flow coming from the chamber formed underneath said adjusting element. When necessary, in the chamber formed underneath said adjusting element, there can be fed gas, such as air, and/or liquid, such as water, in order to advantageously improve the functionality of the apparatus.
Advantageously the adjusting element attached on the bottom of the feed chamber of the material to be heated is a mushroom valve with replaceable wearing parts and sealing. The valve is arranged to operate by the pressure of the gas and/or liquid to be fed in the chamber formed underneath the valve. The mushroom element of the valve rises upwardly by the pressure of the gas or liquid fed in the chamber, in which case the medium flowing from the valve, advantageously a gaseous medium, lifts the possible coarser solid particles of the material to be heated advantageously back to the material flow. On the other hand, the liquid medium to be fed in the chamber is mainly used for preventing the blocking of the apparatus according to the invention, if the velocity of the material to be heated is too low, or if the material to be heated contains particles so coarse that they are not carried along with the flow. Normally the medium that is fed via the chamber located underneath the adjusting element is used in the apparatus according to the invention preferably so that the employed medium is mainly a gaseous medium, which is replaced by a liquid medium or into which there is added liquid medium, when the surfaces of the adjusting element should be washed.